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https://github.com/moses-smt/mosesdecoder.git
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38d790cac0
The code uses two mechanisms for generating random numbers: srand()/rand(), which is not thread-safe, and srandom()/random(), which is POSIX-specific. Here I add a util/random.cc module that centralizes these calls, and unifies some common usage patterns. If the implementation is not good enough, we can now change it in a single place. To keep things simple, this uses the portable srand()/rand() but protects them with a lock to avoid concurrency problems. The hard part was to keep the regression tests passing: they rely on fixed sequences of random numbers, so a small code change could break them very thoroughly. Util::rand(), for wide types like size_t, calls std::rand() not once but twice. This behaviour was generalized into utils::wide_rand() and friends.
44 lines
871 B
C++
44 lines
871 B
C++
#include "util/random.hh"
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#include <cstdlib>
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#include <boost/thread/locks.hpp>
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#include <boost/thread/lock_guard.hpp>
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#include <boost/thread/mutex.hpp>
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namespace util
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{
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namespace
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{
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/** Lock to protect randomizer.
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*
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* This module is implemented in terms of rand()/srand() from <cstdlib>.
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* These functions are standard C, but they're not thread-safe. Scalability
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* is not worth much complexity here, so just slap a mutex around it.
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*/
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boost::mutex rand_lock;
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} // namespace
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void rand_init(unsigned int seed)
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{
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boost::lock_guard<boost::mutex> lock(rand_lock);
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srand(seed);
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}
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void rand_init()
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{
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rand_init(time(NULL));
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}
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namespace internal
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{
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// This is the one call to the actual randomizer. All else is built on this.
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int rand_int()
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{
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boost::lock_guard<boost::mutex> lock(rand_lock);
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return std::rand();
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}
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} // namespace internal
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} // namespace util
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